Матрицы, время исполнения, лаба 3-5

#define _USE_MATH_DEFINES
#include <cmath>
#include <iostream>
#include <ctime>
using namespace std;


int main()
{
    int M, N;
    double string_sum, row_product, duration;

    cin >> M;
    cin >> N;
    row_product = 1;

    double** Matrix = new double* [M];

    for (int i = 1; i <= M; i++)
    {
        Matrix[i - 1] = new double[N];

        for (int j = 1; j <= N; j++)
        {
            Matrix[i - 1][j - 1] = sqrt(i + j);
            //cout << Matrix[i - 1][j - 1] << "\t";
        }

        //cout << endl;
    }

    duration = clock();

    for (int i = 1; i <= M; i++)
    {
        string_sum = 0;

        for (int j = 1; j <= N; j++)
        {
            Matrix[i - 1][j - 1] = sqrt(i + j);
            string_sum += Matrix[i - 1][j - 1];
        }

        row_product *= string_sum;
    }

    duration = clock() - duration;

    cout << "Total product - " << row_product << endl;
    cout << "Time in ticks / secs - " << duration << " / " << duration / (double) CLOCKS_PER_SEC;
}